<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>change-to-flex</title>
    <link rel="stylesheet" href="./reset.css">
    <style>
        .flex-container {
            display:flex;
        }
        .flex-item:nth-child(1){
            background: yellow;
        }
        .flex-item:nth-child(2){
            background: green;
        }
        .flex-item:nth-child(3){
            background: pink;
        }
        .flex-item:nth-child(4){
            background: red;
        }
    </style>
</head>
<body>
    <div class="flex-container">
        <div class="flex-item">A</div>
        <div class="flex-item">B</div>
        <div class="flex-item">C</div>
        <div class="flex-item">D</div>
    </div>
</body>
</html>